Polyurethane roller coating process for carpet backing

ABSTRACT

A method for preparing carpet by using polyurethane to anneal secondary backing to a greige, comprising fibers attached to a primary backing. The polyurethane monomers are mixed just prior to application to the greige primary backing allowing the relatively low viscosity polyurethane to penetrate the fibers of the primary backing to aid in fiber lock. The polyurethane is puddle between two rollers that coat a layer of polyurethane onto the greige. The polyurethane coated greige is then contacted with the secondary backing before complete polymerization to insure sufficient tack to hold the backings together resulting in a durable carpet requiring a relatively low weight of polyurethane monomers.

The present application claims priority to the May 25, 2004 filing dateof U.S. provisional patent application, Ser. No. 60/574,112.

FIELD OF THE INVENTION

The present invention relates to improved methods for adhering secondarybacking to tufted or woven carpeting greige employing polyurethaneadhesive systems.

BACKGROUND OF THE INVENTION

Polyurethanes are produced in four different principal forms includingelastomers, coatings, flexible foams, and cross-linked foams.Polyurethane foams are produced by reacting isocyanate compounds withpolyol compounds generally in the presence of catalysts, surfactants,and other auxiliary agents. At the start of polyurethane foamproduction, the reactive raw materials are held as liquids in large,stainless steel tanks. These tanks are equipped with agitators to keepthe materials fluid. A metering device is attached to the tanks so thatthe appropriate amount of the reactive material can be pumped out.Generally, the ratio of polyol to isocyanate is about 2:1; and the ratioof components is strictly metered to control the characteristics of theresulting polymers. The reacting materials are then mixed and dispensed.Reaction between the isocyanate and the polyol, usually referred to asthe gel reaction, leads to the formation of a polymer of high molecularweight. This reaction increases the viscosity of the mixture andgenerally contributes to cross-link formation. The second major reactionoccurs between isocyanate and water. This reactive produces carbondioxide gas which promotes foaming causing the volume of the urethanepolymer to grow. In some instances, auxiliary blowing agents are addedto further increase the volume of the polymer.

Both the gel and blow reactions occur in foams blown partially ortotally with carbon dioxide gas. In order to obtain a good urethane foamstructure, the gel and blow reactions must proceed simultaneously and atoptimum balance rates. For example, if the carbon dioxide generation istoo rapid in comparison with the gel reaction, the foam tends tocollapse. Alternatively, if the gel reaction is too rapid in comparisonwith the blow reaction generating carbon dioxide, the rise of the foamwill be restricted resulting in high density form. In practice, thebalancing of these two reactions is controlled by the natures ofcatalysts and auxiliary agents used in the process.

It is customary in the carpet and rug industry to use various forms offilled and unfilled latex or polyurethane to coat the back of carpet.The coating is used to bond the face fibers to the primary backing andalso thereby creating good tuft bind or fiber lock, and to bondsecondary backing material to the greige (fibers/primary backing). Forexample, carpets having attached polyurethane layers as backing aredescribed in U.S. Pat. Nos. 3,755,212; 3,821,130; 3,862,879; 4,022,941;4,515,646; 5,604,267; 5,908,701; and 6,299,715. A key property of thecarpet produced by these methods is annealing strength, or the forcerequired to delaminate or separate the secondary backing from thecarpet. In order to achieve optimal annealing strength, the secondarybacking must be in direct contact with the greige, and a sufficientamount of adhesive must be between the greige and the secondary backingto thoroughly wet the fibers. A second key property is fiber lock, or ameasure of the force necessary to pull face fibers from the carpet.

The most widely used annealing adhesive is latex. Latex is typicallyapplied by methods involving roll over flatbed or roll over rollprocesses. Regardless, of the method used, the greige is coated with anadhesive precoat of latex, and the secondary backing, also coated withlatex, is married to the greige and cured.

Although, latex is a popular adhesive, carpet prepared from latexdisplays numerous shortcomings. For example, the strength and hydrolyticstability of latex is less than desired, and latex is less durable overtime than alternative polymer systems such as PVC plastisol orpolyurethane. Moreover, latex curing requires the evaporation of largeamounts of water during cure, a process that is both expensive andenergy intensive. Heating latex annealed carpet to achieve timely curingrequires temperatures in at least the range of 70° C., and thesetemperatures may cause some carpet fibers and backing materials toshrink or change appearance and properties. To minimize the cost oflatex adhesives, substantial quantities of filler material are added.The use of latex filler hinders the effective recycling of manufacturingremnants and used carpet at the end of its life cycle.

Alternatively, polyurethane adhesives have been employed to form carpetwith superior annealing strength and other desirable physicalproperties. However, despite the advantages of polyurethane, cost andtechnical problems have kept it from widespread use in the industry as acoating, and even more rarely as a flexible foam.

Attempts to replace latex with polyurethane have resulted in a varietyof new problems, requiring modifications to the usual latex annealingprocess. One striking example is the difficulty associated with placingpolyurethane onto a greige material, while maintaining the necessaryadhesiveness to attach the second backing. After the pre-polymers havebeen mixed and polymerization begins polyurethane soon begins to loseits adhesive properties. In addition, because the blow reactionsubstantially increases the volume of the polyurethane layer, even smallirregularities in the application of the polyurethane components to thegreige may result in unacceptable variations in the depth of theresulting polyurethane foam layer.

Loss of adhesiveness is generally not a problem with the use of latex.Conventional latex maintains its adhesiveness and viscosity duringprocessing, even into the curing oven. Following application of latexadhesive to both the greige and the secondary backing the two componentsare married and as a result of the latex properties, good temporaryadherence of the secondary backing to the greige is observed. In thecuring oven, the latex viscosity does not drop significantly as asignificant portion of water is evaporated. Thus, the secondary backingsatisfactorily adheres to the greige.

On the other hand, polyurethane application from bulk troughs, common inlatex systems, is made very difficult due to premature polymerization inthe delivery line. Typically, polyurethane is applied as “froth,”polymerized prior to application and dispensed on the primary orsecondary backing before the upstream edge of a doctor blade. However,unless the manufacturer guards against premature polymerization thedelivery line becomes clogged, thereby retarding the flow ofpolyurethane to the dispensing apparatus. The doctor blade will alsotend to foul with polyurethane that adheres and cures. In additionpolyurethane begins to lose its adhesiveness soon after polymerizationbegins unless the manufacturer controls the polymerization rate by usingheat sensitive catalysts or other chemical agents designed to maintainthe viscosity of the polyurethane. Regardless of the manufacturer'sattempts at controlling premature polymerization, the manufacturer hasonly a finite amount of time after the pre-polymers (polyol andisocyanate) have been mixed in which to apply the polyurethane andcontact the greige to the backing before the polymer begins to lose itsadhesive properties.

When chemical agents are added to control premature polymerization andmaintain viscosity to enable the polyurethane to penetrate the fibersand achieve good tuft bond and maintain adhesiveness to affix thesecondary backing, the resulting mixture typically will not cure quicklywithout oven curing. Oven curing adds time and cost to the finishingprocess, and will also adversely affect some fibers by matting orshrinkage.

In an attempt to combat the rapid loss of adhesiveness manufacturershave applied one coating of polyurethane to the greige as fiber lock anda second coating of polyurethane just prior to contacting the secondarybacking to insure sufficient adhesion between the backings. Even withthe additional polyurethane, the slow advancement of most commercialcarpet lines, and the inherent lack of adhesiveness associated withpolyurethane, does not allow for the desired adherence between thegreige and the secondary backing without the use of considerable andexpensive quantities of the pre-polymers.

To extend the coverage of a given quantity of pre-polymers, it iscustomary to add filler material to the mixture. However, fillermaterials are generally abrasive and complicate the application of thepolyurethane mixture by either wearing on applicator parts or increasingthe tendency of lines and applicators to clog or apply unevenly.

Curing the backing to the greige is also complicated because of theconsiderable decrease in viscosity of the polyurethane prior to cure.The viscosity of the polyurethane, and likewise its adhesiveness, maydecrease to only 10% of its initial value prior to application of thesecondary backing as the catalyzed polyurethane-forming reaction beginsto exert its effect. The greatest decrease in viscosity is oftenexhibited over the temperature range from ambient to about 70° C., wherethe polyurethane catalysts are not optimally active. As a result, if theinitial adherence of the secondary backing to the greige is insufficientthe secondary backing may separate during this period of low viscosity.

In an attempt to address the problems associated with the use ofpolyurethane several changes to the underlying process have beendisclosed. For example, U.S. Pat. No. 6,264,775 offers the addition ofvarious chemical thickening agents to the polyurethane to maintainviscosity and adhesiveness. Another process provides for the use ofmultiple applications of polyurethane to the primary backing prior tojoining the secondary backing. See e.g., U.S. Pat. No. 6,299,715. Stillanother technique disclosed in U.S. Pat. No. 6,299,715, is theapplication of both polyurethane to the primary backing and anothertacky composition to the secondary backing prior to joining the twobackings. In U.S. Pat. No. 4,515,646, two of the present inventors eventried to use refrigerated isocyanate and polyol components withoutcatalysts to prevent premature polymerization. Commonly owned WO03/039869 proposed spraying a substantially water-free polyurethane onthe griege and effecting the blow and curing with steam. None of thesetechniques have been favored over standard latex based carpet laminates,primarily due to the increased cost and complexity associated withbuilding and using separate manufacturing lines to implement the newtechnologies, or the failure of the techniques to work in a productionenvironment.

It would therefore be desirable to provide a polyurethane foam carpetannealing process requiring only a single application of thepolyurethane, while providing acceptable fiber lock and annealingstrength. It would also be desirable to provide a polyurethane annealingsystem which does not require excessive quantities of polyurethane toprovide sufficient annealing strength. It would be beneficial to providea polyurethane annealing system which does not require an oven forcuring.

SUMMARY OF INVENTION

The present invention pertains to a polyurethane carpet annealing systemwhich discloses several unique advantages over the prior art. First itrequires only a single application of polyurethane. The lower amount ofpolyurethane employed in a single application significantly decreasesthe weight of the carpet and decreases raw material costs. Second, thepolyurethane is blown and cured at near ambient temperatures, optimallyutilizing only heating drums and possibly steam. The absence of anoven-curing step markedly decreases the time from application of thepolyurethane to product roll-up. Third, one source of water for the blowreaction may be from steam applied to the polyurethane ingredients afterthey have been dispersed upon the greige. Fourth, the polyurethane isapplied from a puddle between two rollers over the greige and one ofthese rollers may also advantageously serve to press the polyurethaneinto the greige. Fifth, a vacuum, blower, ultra sonic system, orcombination of these may be employed, preferably prior to anyapplication of steam or heating drums to increase the penetration of thepolyurethane ingredients into the greige. The carpet produced by theprocess exhibits acceptable fiber lock and initial secondary backingadhesion without the use of large quantities of polyurethane and withoutthe expensive oven curing step common in other annealing systems.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a typical prior art latex-based carpet annealingprocess.

FIG. 2 illustrates the roller-delivered polyurethane coating process ofthe present invention

FIG. 3 illustrates a roller arrangement for applying polyurethane to thegreige goods.

FIG. 4 is an alternative configuration of the roller-deliveredpolyurethane coating process of the present invention.

FIGS. 5A-5D are yet other alternative configurations of theroller-delivered polyurethane coating process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is designed to improve the annealing of secondarybacking to tufted or woven carpeting utilizing a polyurethane adhesivesystem. Referring now to the drawings in more detail, FIG. 1 illustratesa typical prior art commercial latex-based carpet annealing process. Thegreige 5, with top carpet face 14 and bottom primary backing side 15 towhich fiber lock adhesive is applied, is directed by rollers 20 to placethe primary backing side 15 of the greige under trough 25, which issupplied with latex through line 30. The downstream edge of trough 25serves as a doctor blade 35, in conjunction with plate 40. The doctorblade 35 is used to both even the application of latex and assist inpressuring latex into the primary backing. Adjusting the amount of latexapplied also serves to adjust the force applied to urge the latex intothe primary backing 15 and into the fibers of the tufted yarns andprimary backing. Further penetration is provided by pressure roller 45.The carpet is then redirected by roller 50. Secondary backing 55 issupplied from roll 60 and directed by rollers 65 across wheel-roll 70,which rotates in trough 75 filled with additional latex which coats thesecondary backing 55. The coated secondary backing 77 is pressed ontothe latex-coated greige 80 by travel through ligation rolls 85. Thecarpet then passes through oven 90 where water is removed from thelatex, and the latex cures, adhering fibers and secondary backing toform a lamellar carpet. The resulting carpet is relatively inexpensiveto manufacture and provides adequate tuft bind and resistance todelamination, but suffers from the previously mentioned shortcomings oflatex backed carpets.

It will be understood that in most prior art polyurethane backings,water is not added to the froth and the resulting polyurethane backingis not “blown,” the only volume in the backing layer having beeninjected in the form of air in the froth. The present invention isdirected to a flexible polyurethane foam that is blown, rather thanmerely a polyurethane coating.

FIG. 2 illustrates a preferred dispensing apparatus for applying mixedpolyurethane onto the greige. The greige 11, is fed in direction 12 pastthe dispensing apparatus 10. The dispensing apparatus 10 preferablycomprises a polyurethane dispensing head 21, fed by a polyol tank, aniso tank, and a catalyst tank. Optimally, catalysts and other additivesmay be selected that can be premixed with one of either the polyol oriso mixtures.

Polyol tank contains polyol mixed with filler and surfactants, such assilicone. The iso tank contains isocynate. The catalyst tank containsone or more catalysts and a small amount of water. Typically, there willbe between two hundred fifty and five hundred parts filler per hundredparts of polyol and between about 0.05 to 3.0 parts of water per hundredparts of polyol. Contents of the polyol, iso and catalyst tanks arepumped to polyurethane coating head 21. The temperature of the polyolmixture may be controlled either by refrigerating the entire polyol tankor by passing tubing from the tank through a heat exchanger to achievethe desired temperature prior to mixing.

All of the ingredients may be temperature controlled as described inconnecting with the polyol mixture above. In addition, there may beother additives such as stabilizers, antioxidants, antimicrobials,anti-mildew agents, colorants, flame retardants, penetrants, and chainextenders, all depending upon the characteristics desired in theresulting foam.

The illustrated polyurethane coating head 21 dispenses polyurethanemixture into a puddle 24 extending across a substantial width of thegreige 11. The puddle 24 is formed by the proximity of applicationroller 23 and drive roller 26. In the illustrated embodiment, theapplication roller 23 turns clockwise pulling a polyurethane coatingdownward from the puddle onto the greige 11. The thickness of thepolyurethane coating applied may be adjusted by speeding the rotation ofthe application roller 23 to bring down more polyurethane. The greige 11may be pressured against one or both of application roller 23 and driveroller 26 by support 27. Preferably the greige 11 passing over thesurfaces of application roller 23 and drive roller 26 effects a wipingaction on the rollers 23, 26 and minimizes polyurethane buildup. Wipingaction is naturally effected on application roller 23 because it rotatesits surface in the opposite direction to the travel of the greige 11.Wiping action on the drive roller 26 is preferably effected by rotatingthat roller somewhat faster than the greige 11 is allowed to travelthrough the secondary backing process.

The adhesion of the polyurethane material to the greige 11 may befurthered by the use of a roller, a doctor blade, controlled vacuum,blower, ultrasonic waves or an air knife, and in some instances, bythinning the viscosity of the polyurethane material. An ultrasonicallyvibrated doctor blade is preferable when actually contacting thepolyurethane material as the vibration tends to prevent adhesion andbuildup on the doctor blade. Penetration into the greige is critical toachieving acceptable tuft bond and annealing strength.

By placing the mixing directly at the polyurethane dispensing head 21closer to the actual application of the polyurethane components, thereis less time for a reaction to occur before the components are on thegreige 11, thereby reducing the chance of clogging the dispensingapparatus. The head 21, or preferably a plurality of transversely spacedheads 21, may move laterally across the greige 11 between theapplication roller 23 and drive roller 26 to keep the puddle 24relatively even. Even-with this arrangement, the polyurethane mixturemay be thick and viscous so that an extremely strong or reinforcedassembly is useful in supporting the rollers 23,26 to prevent theirlongitudinal movement.

FIG. 2 illustrates the carpet finishing process according to the presentinvention. The greige 11 with carpet face 10 downward is fed onto atenter roll 13 that directs the greige 11 to rollers 23, 26 of thedispensing apparatus 10, and the carpet face 14 is advanced over thesupport 27 using pulling rollers 16.

In FIG. 2, a layer of polyurethane polymer is deposited onto the primarybacking side 15 as it passes over support 27 using rollers 23, 26.Preferably, the polyurethane is applied to the primary backing 15 at anarea concentration of 3 to 5 ounces of polyurethane or about 6 to 40ounces total mixture including fillers and additives per square yard orin a more preferred concentration of about 14 ounces total mixture persquare yard. The 3 to 5 ounce per square yard range is the weight ofonly the polyurethane components, and does not include the weight ofoptional additives such as fillers or thinners that are useful aids toeffective and economical coverage. The polyol and isocyanate pre-polymercomponents are laid onto the primary backing 15 by application roller23. The pre-polymers are preferably mixed just prior to dispensing fromthe polyurethane dispensing head 21 and subsequent application to theprimary backing 15.

At this time, only a small amount of water is added which reacts andserves as a blowing agent. According to this method, the polymerizationprocess does not begin to occur until just prior to the exit of thepolyurethane components from the polyurethane dispensing head 21, andthe polyurethane is quickly applied by rollers 23, 26 to the backing 15.This process and pressure between application roller 23 and/or driveroller 26 and support 27 allows the relatively low viscositypolyurethane to deeply penetrate the fibers in the primary backing,resulting in excellent fiber lock characteristics. Immediately afterapplication of the polyurethane, optional aids to penetration such asthe previously mentioned doctor blades, vacuums, or blowers may be mosteffectively employed as may be particularly desired when processinggreige tufted with heavy yarns.

The polyurethane coated greige 11 is then optionally passed across asteam box 150, that is adjustable with respect to steam temperature,volume, and slot size. Steam box 150 adds more water to facilitate theblow reaction and heat to aid in accelerating the gel reaction. Inaddition the steam serves to enhance blooming of the yarns passingthrough the primary backing for deeper penetration and assures a morelevel coverage of polyurethane. A fume hood 155 is placed above thesteam box 150 to capture escaping volatiles released with the steam.Conspicuously absent at this stage of the process is an oven curingstep. Heat may also be applied to the carpet by passing it around oil orsteam heated drums. An oven is not necessary in the process because thepolyurethane components are essentially kept separate until they areapplied to the primary backing 15, therefore there is no need to dopethe polyurethane components in order to severely slow the rate ofpolymerization. However, rather than as illustrated, steam or other heatis preferably applied after the coated greige 11 is joined with thesecondary backing 55 unless it is necessary to advance the polyurethanecuring reaction before marriage of the greige 11 with the secondarybacking 55.

In a preferred embodiment of the present process temperatures aregenerally maintained within 40° C. of ambient temperature or in a morepreferred embodiment within 20° C. of ambient temperature during thecarpet manufacturing process. In contrast, prior art polyurethane curingprocesses are required to utilize heat sensitive catalysts and otherchemical additives to maintain sufficient viscosities to apply thepolyurethane, from various holding lines and troughs, to the backingsurface. These additives, and the absence of water, necessitate a heatcuring stage.

After applying the polyurethane coating, and preferably before steamingor otherwise heating the coated greige 11, the coated greige 11 israpidly pulled to merge rolls 160 a, 160 b where the secondary backing55, supplied from roll 60, contacts the coated greige 11. Due to theshort time that elapses between the initial application of polyurethaneand the merger of the secondary backing 55 with the coated greige 11,the polyurethane possesses sufficient tackiness to anneal the secondarybacking in place.

The merge rolls 160 a, 160 b may not only contact the secondary backing55 to the coated greige, but also serve to gauge the height of the blownpolyurethane, preferably at no more than about one-eighth inch inheight, and to halt any additional volumization of the polyurethane.This is due to the merge rolls 160 a, 160 b compressing the blownpolyurethane and rupturing many of the still closed cells within thepolyurethane. In a preferred embodiment, the secondary backing is a spunbonded fabric of nylon, polypropylene, polyester, polyethylene orsimilar fibers and may have a calendared surface. A spun bond fabrichaving a weight of between about 1.5 and 4 ounces per square yard is asuitable and inexpensive secondary backing. The absence of an ovencuring step facilitates the use of relatively low melting pointmaterials.

The independence gained by controlling the mixing of polyol andisocyanate has led to the removal of a curing station. The excision ofthis step has dramatically improved the processing speed of laminatedcarpets, cutting manufacturing time by as much as 50-60% withoutsacrificing the annealing strength or fiber lock properties of thecarpet. The annealed carpet can then be cooled briefly on accumulatorrolls 190 and rolled on take up roll 200 for storage and transport,typically in lengths of up to about 600 feet.

A number of variations to the described process are possible. Forinstance, the carpet may be fed over a vacuum or ultra sonic wave devicein order to pull the viscous polyurethane deeper into the primary carpetbacking after application of polyurethane by application roller 23.Also, if the heat from the steam box 150 is used prior to joining thegreige 11 to the secondary backing 55 and the steam acceleratespolymerization so that the polyurethane film has cured sufficiently tolose much of its tackiness, the secondary backing 55 may require coatingto enhance its adherence to the coated greige product 11.

The secondary backing 55 may also be applied at a much earlier stage inthe process. In fact, immediately after the polyurethane layer isdeposited on the backing side 15 of the greige as it passes under thedrive roller 26, the secondary backing 55 may be applied, preferably bytransition around a doctor bar or merge roller which causes thesecondary backing 55 to come into contact with the polyurethane layer asthe reaction of the prepolymers is just beginning. However, as discussedbelow, use of an intermediate station to enhance penetration of thepolyurethane into the fibers of the primary backing and back stitches ofthe tufted yarns is frequently performed prior to applying the secondarybacking. The polyurethane achieves much of its reaction between theprimary backing side 15 and the secondary backing 55 and the use ofsteam box 150 and fume hood 155 accelerates this process and providesadditional water to the reaction. Again passing under merge rollers 160a, 160 b crushes the backing and effectively halts the foaming processso that the polyurethane layer does not gain additional height. Thecuring process is completed as the carpet passes through accumulator 190and is finally wound on a master carpet roll 200.

FIG. 3 shows an example of roller coating station 10 in greater detailwith greige goods 11 passing over first directional roller 116 a,downward and around clockwise driven application roller 23 andcounterclockwise driven drive roller 26 upward to second directionalroller 116 b. Spacing between application roller 23 and drive roller 26is adjustable utilizing linkage 123. As the greige 11 passes beneathrollers 23, 26 polyurethane is applied from puddle 24. Polyurethanepuddle 24 is dispensed from dispensing head 21 which is preferably a mixhead mounted for transverse movement where feed from a polyol tankincluding polyol and other ingredients typically including filler andcatalyst is combined with isocyanate and additional catalyst. The numberof dispensers 21 can vary and typically one mix head and dispenser foreach meter in width of carpet is preferable. The polyol and isocyanatematerial coming to the mix head should stay at a constant temperatureduring the processing of a lot of greige. The preferred temperature isabout 50° C., but in connection with some polyurethane mixtures and somecarpet products, optimal results may be obtained at higher or lowertemperatures. The temperature 50° C. is utilized to thin or lower theviscosity of the polyurethane mixture coming from the dispenser 21 andimprove the penetration of the polyurethane in the primary backing andback stitches of the yarns of the greige 11. Because of the tendency ofpolyurethane to adhere to surfaces that it contacts, pressurized air isa preferred method of containing and shaping the polyurethane in thepuddle 24.

The application roller 23 and drive roller 26 are precision rollersdesigned to apply the polyurethane material evenly across the width ofthe greige 11 and to maintain a consistent rate of application ofpolyurethane to each square yard of carpet. Because the length of therollers is typically approximately four meters, and up to six meters insome cases, special construction may be necessary to keep the gapsbetween rollers 23, 26 even over their full length. In order to keep thepuddle 24 between the rollers 23, 26, one roll runs clockwise and theother roll runs counterclockwise. In the embodiment illustrated in FIG.3, the application roller 23 runs clockwise and the drive roller 26 runscounterclockwise, and it is preferred to have the clockwise roller runat a slower speed than the speed at which the greige 11 is fed while thecounterclockwise roller runs faster. It will be understood that rollerspeeds will vary depending upon the construction of the greige productand the amount of polyurethane material to be applied. For instance,loop pile greige goods are generally easier to process to achieve goodtuft bind and delamination strength than cut pile goods. In addition,greige tufted with finer yarns is generally more easily penetrated by apolyurethane mixture than greige tufted with thick or berber-like yarns.

The rollers 23, 26 can be run at a variety of speeds as long as therollers wipe themselves clean, generally by the feed rate of theprocessed greige 11 being either faster or slower than the speed ofrotation of rollers 23, 26, and thereby avoid any buildup on therollers. The amount of polyurethane material applied from puddle 24 isdetermined by speed of the rollers 23, 26, the width of the gap betweenthe rollers, and the viscosity of the polyurethane material. It isgenerally preferred that the viscosity of the polyurethane material beconstant and the gap between rollers 23, 26 be kept constant and anychanges in the amount of polyurethane material applied being controlledby changing roller speeds. However, adjustments to roller spacing orviscosity may be preferable in some instances.

In FIG. 3, a support roller 127 is also shown in order to apply upwardpressure against the greige 11. The pressure applied by roller 127 isadjustable by controlling piston 128 that communicates upward pressureto the ends of roller 127 by means of linkage 129. The pressure appliedby support roller 127 also affects the amount of polyurethane materialbeing applied to the greige 11 and the pressure should be set at aconstant during a run of carpet. Certain greige products will require adifferent pressure setting from the support roller 127 for optimalperformance.

Turning then to FIG. 4, an alternative arrangement of the polyurethaneroller applied backing system is illustrated. The greige goods 11proceed about a J-box 92 to assist in controlling the carpet's entryinto the roller applicator 10. After the greige 11 is coated withpolyurethane, it passes by ultrasonic doctor blade 36 where theultrasonic vibrations of the doctor blade prevent adhesion of thepolyurethane material which would foul the blade and the pressure of thedoctor blade 36 improves the penetration of the polyurethane mixture.The greige 11 then passes over steam box 150 and below fume head 155 andthereafter immediately has secondary backing 55 married to it by pinchrollers or nip rolls 160 a, 160 b. Thereafter, the carpet passes to aheated drum such as heat can 40 which is preferably a hot oil can butcould also be steam heated. Heat can 40 helps iron the secondarymaterial 55 to the greige 11 and also accelerates the cure processallowing the carpet to be run at higher speeds and in a shorter distanceto roll-up. The number and size of heat cans 40 may vary depending uponthe run speed and space desired. No heat can 40 is required asadditional heat is not necessary for curing a polyurethane mixture,merely time, and tenter frames and accumulators may be utilized ifnecessary. Indeed, after passing about heat can 40, the carpet is shownproceeding to tenter system 52 and accumulator 190 and thereafter to theroll-up of the finished carpet 200.

The timing of the marriage of secondary backing 55 to the coated greige11 is critical. The reaction of the polyurethane material must besufficiently complete to marry the secondary backing 55 to the greige11. There is a relatively brief window in which the polyurethanematerial is sufficiently sticky to form a strong bond to the greige 11.If the greige 11 arrives too early, the adhesion to the backing 55 andresulting overall product will not be as strong as possible. Similarly,if the greige 11 arrives too late at the marriage point, thepolyurethane material will be over-cured and the secondary backing 55will not stick to the greige 11. The state of reaction of thepolyurethane material at the marriage point can be changed by addingheat to the greige prior to the marriage point, changing the catalystpackage to accelerate or decelerate reaction and curing, or adjustingthe distance between the application rollers 23, 26 and the marriagepoint. In the embodiment of FIG. 4, it is preferred to utilize astandard catalyst package, a standard distance to the marriage point,and to adjust the heat and water applied by the steam box 150 toincrease the heat and accelerate the reaction as necessary or shut offthe heat and slow the reaction, in order to have the polyurethanematerial at the appropriate state to marry the greige 11 with thesecondary backing 55.

The embodiments of FIGS. 5A-5D illustrate alternative constructions thatadjust the state of reaction of the polyurethane material at themarriage point by providing a method to adjust the distance between theapplication rollers 23, 26 and marriage point. Specifically, theunbacked greige 11 is passed through tenter frame 91 and J-box 92 tocondition and control the greige prior to application of thepolyurethane material. The greige 11 proceeds past application rollers23, 26 and then to a moveable tenter roll 147 adjustable between a lowposition 47 and a high position 247 shown in phantom, and theillustrated intermediate position 147 to allow the length of coatedgreige 11 intermediate the application rolls 23, 26 and nip rolls 160 a,160 b at the marriage point with secondary backing 55 to be increased ordecreased and thereby effect the completeness of the reaction of thepolyurethane material at the marriage point. Either nip rolls 160 a, 160b or subsequent rubber coated pressure rolls 66 a, 66 b should bepressure controlled to ensure a complete marriage of the secondarybacking 55 to the coated greige 11. Thereafter the carpet again passesaround first heat can 40 and second heat can 41 to iron the secondarybacking 55 to the greige 11 and speed the curing process. The carpetthen goes through accumulator 190 to roll-up as the finished carpetproduct 200.

FIG. 5B illustrates the polyurethane application, marriage and heatingof the FIG. 5A in greater detail. FIG. 5C illustrates an alternativeconstruction of the embodiment of FIG. 5B wherein the support rolls 127,137 in the support or backup structure 27 of FIG. 5B are replaced by airbladder 227. The air bladder 227 can more closely conform to the shapeof the application and drive rollers 23, 26 and preferably urges aTeflon belt or other low friction material against the face 14 of thegreige 11 and provides good results for some products. Again, themoveable tenter roller 147 controls the distance between the applicationof polyurethane material and the marriage point at pinch rollers 160 a,160 b and the carpet proceeds around first and second heat drums 40, 41which are typically heated to at least 70° C., and are optimally kept ata temperature of about 85° C. to 90° C.

Finally, FIG. 5D shows yet another alternative configuration for theapplication of polyurethane material through rollers 23, 26. Again, thegreige passes about tenter frame 91 and J-box 92 prior to proceeding topolyurethane dispensing apparatus 10. The greige 11 can be additionallyconditioned by passing through a pattern straightener or steam box ifdesired. The greige 11 then proceeds beneath rollers 23, 26 which supplypolyurethane material from puddle 24. Penetration of the polyurethanematerial is increased by the pressure of ultrasonic doctor blade 36against the coated greige 11 as it passes over support roller 64. Thenblower 37 and vacuum 38 also act upon the polyurethane material toincrease penetration of the fibers of the yarn back stitch and anyprimary backing fabric comprising the greige. Moveable tenter roll 147controls the distance between the polyurethane application apparatus 10and marriage point at nip wheels 160 a, 160 b and the reaction time ofpolyurethane materials can be additionally controlled by the temperatureof the air applied from blower 37. The carpet again proceeds around heatcans 40, 41 to iron the secondary backing 55 to the greige 11 andaccelerate the cure process. In some cases, shearing machines, trimmers,and other finishing equipment can be located between heat cans 40, 41and roll up.

In the foregoing embodiments, the Figures have been simplified forclarity and to ease viewing and understanding. In commercialembodiments, additional devices, e.g. drive motors, tension devices,etc. will be required.

Polyurethane prepolymers useful in the practice of the present inventionare prepared by the reaction of active hydrogen compounds with anyamount of isocyanate in a stoichiometric excess relative to activehydrogen material.

The prepolymer formulations of the present invention include a polyolcomponent. Active hydrogen containing compounds most commonly used inpolyurethane production are those compounds having at least two hydroxylgroups or amine groups. However, any active hydrogen containing compoundcan be used with the present invention, and indeed some soy based oilscan be used.

In the practice of the present invention, preferably at least 50 weightpercent of the active hydrogen compounds used to prepare thepolyurethane is a polyol having molecular weight of from about 100-400.

The polyisocyanate component of the formulations of the presentinvention can be prepared using any organic polyisocyanates, modifiedpolyisocyanates, isocyanate based prepolymers and mixtures thereof.These can include aliphatic or aromatic isocyanates. Preferably theisocyanate used to prepare the prepolymer formulation of the presentinvention is methyl diisocyanates such as Bayer's 142L or Dow p901 orblends of equal type.

Catalysts suitable for use in preparing the polyurethane of the presentinvention include tertiary amines, and organometallic compounds andmixtures thereof. For example, suitable catalysts include stannousoctoate, triethylenediamine, N-methyl morpholine, like compounds andmixtures thereof. The catalysts do not necessarily need elevatedactivation temperatures or other promoters to initiate polymerization.

Surfactants can be useful for preparing a stable dispersion of thepresent invention. Surfactants useful for preparing a stable dispersioncan be cationic, anionic, or non-ionic surfactants. Preferably thesurfactants used to prepare the prepolymer formulation of the presentinvention are silicone surfactants such as Dow Corning DC-194 or UnionCarbide's L-540. A surfactant can be included in a formulation of thepresent invention in an amount ranging from about 0.01 to about 7 partsper 100 parts by weight of polyurethane component.

A compound of the present invention optionally includes a fillermaterial. The filler material can include conventional fillers such asmilled glass, calcium carbonate, aluminum trihydrate, barium sulfate,fly ash, dyes and pigments or fire retardants (aluminum trihydrate andTris polyolefin glycol). Preferably the filler can be present in anamount ranging from 0 to 600 parts, and more preferably between 100 and500 parts, per 100 parts of the polyol component. With the use ofthinning and penetration enhancing additives, it is possible to achievesatisfactory results with as much as 550 to 600 parts filler to 100parts of polyol. According to the invention, utilizing greige goodscomprising a backing fabric tufted with level loop yarns and theapplication of polyurethane materials containing a combination ofpolyol, isocyanate, and catalyst at a rate of 90 grams per square yard,together with fillers, penetrants and other extenders, the resultingcarpet achieves a tuft bind of at least 6.25 pounds measured accordingto ASTM standards and delamination strength in excess of at least 2.5pounds. Indeed, when using spun bonded polypropylene secondary backingmaterial, which is possible due to the absence of oven curing, thesecondary backing will often tear prior to delamination. When the samerate of 90 grams of isocyanate, polyol and catalyst per square yard isapplied to greige comprising a backing fabric tufted with cut pileyarns, the tuft bind exceeds 3 pounds per square inch and delaminationstrength again achieves at least about 2.5 pounds per square inch. Whenthe rate of application of the isocyanate, polyol and catalyst materialis at the rate of 150 grams per square yard, the tuft bind of level loopcarpet may reach 15 pounds and the resulting carpet far exceeds allcustomary structural standards required for residential or commercialcarpet. Furthermore, the resulting carpet utilizing the polyurethanebinder to attach the secondary backing is mold and mildew resistant,non-allergenic, easier to install, and less subject to degradation whensubjected to extreme heat and cold. In addition, the manufacturingprocess utilizes a minimal amount of water compared to the process ofutilizing a latex binder, utilizes less energy, and results in lesswaste products.

Generally, any method known to one skilled in the art of preparingpolyurethane froths can be used in the practice of the present inventionto prepare a polyurethane froth suitable for preparing a carpet of thepresent invention, however, typically only one of the prepolymermixtures is frothed, since the use of water as a blowing agent providesample volume to the polyurethane. It is also possible to froth thepolyurethane mixture in the mix head by adding air or inert gas at thatpoint.

Although a preferred embodiment of the present invention has beendisclosed herein, it will be understood that various substitutions andmodifications may be made to the disclosed embodiment described hereinwithout departing from the scope and spirit of the present invention asrecited in the appended claims.

1. A method for preparing carpet utilizing polyurethane foam to anneal asecondary backing to a greige, having a face and an opposed backstitchside, said process comprising: (a) introducing polyol from a firstsource and isocyanate from a second source, together with a filler and acatalyst to create a polyurethane mixture; (b) creating a puddle of thepolyurethane mixture between an application roller and a drive rollerpositioned transversely and adjacent to the backstitch side of thegreige; (c) applying said polyurethane mixture with at least one of thesaid rollers as the greige is moved laterally with respect to therollers to form a coating on the backstitch side of the greige thatbegins to cure into a polyurethane foam; and (d) contacting a secondarybacking to the polyurethane mixture coated backstitch side of thegreige.
 2. The method of claim 1 wherein the polyurethane mixture isapplied to the backstitch side of the greige at a rate of between 6 and40 ounces per square yard.
 3. The method of claim 1 wherein thesecondary backing is a spun bond polypropylene fabric.
 4. The method ofclaim 1 wherein the secondary backing is a spun bond fabric having aweight of between 1.5 and 4 ounces per square yard.
 5. The method ofclaim 1 comprising the additional step of urging the polyurethanemixture to penetrate the backstitch side of the greige with at least oneof an ultrasonic doctor blade, a blower, and a vacuum, prior tocontacting the secondary backing to the polyurethane mixture coatedbackstitch side of the greige.
 6. The method of claim 1 comprising theadditional step of applying steam to the polyurethane mixture coatedgreige.
 7. The method of claim 1 comprising the additional step ofmarrying the secondary backing to the greige by passing the contactingsecondary backing and greige between a pair of merge rollers biasedtoward one another.
 8. The method of claim 1 comprising the additionalstep of gauging the height of the polyurethane foam formed by the curingpolyurethane mixture by passing the contacting secondary backing andgreige between a pair of merge rollers biased toward one another.
 9. Themethod of claim 1 wherein filler is introduced into the polyurethanemixture at a rate of between 100 and 600 parts of filler per 100 partsof polyol.
 10. The method of claim 1 wherein filler is introduced intothe polyurethane mixture at a rate of between 250 and 550 parts offiller per 100 parts of polyol.
 11. The method of claim 1 wherein thelength of greige between the application of the polyurethane mixture andthe contacting of the secondary backing to the greige is adjustable. 12.The method of claim 1 wherein the puddle of the polyurethane mixture isshaped with forced air.
 13. The method of claim 1 wherein thepolyurethane mixture is created in a mix head and fed to a dispensinghead to deliver the polyurethane mixture to the rollers.
 14. The methodof claim 13 wherein the dispensing head is moveable transversely withrespect to the greige.
 15. The method of claim 1 comprising theadditional step of passing the contacting secondary backing and greigeover at least one heated drum.
 16. The method of claim 15 wherein thedrum is heated to at least 70° C.
 17. A laminated carpet productcomprising: (a) a greige having a face and an opposed backstitch side;(b) a layer of polyurethane foam on the backstitch side comprisingpolymers resulting from the reaction of polyol and isocyanate togetherwith filler and auxiliary agents; (c) a secondary backing materialadhered to the backstitch side by the layer of polyurethane foam;wherein the weight of the polymers resulting from the reaction of polyoland isocyanate is less than five ounces per square yard of carpet andthe delamination strength of the carpet is at least 2.5 pounds of forceper inch.
 18. The laminated carpet product of claim 17 wherein thesecondary backing material is a spun bond polypropylene fabric.
 19. Thelaminated carpet product of claim 17 wherein the secondary backing is aspun bond fabric having a weight of between 1.5 and 4 ounces per squareyard.
 20. The laminated carpet product of claim 17 wherein the greigecomprises a tufted primary backing with a loop pile face and the tuftbind is an average of at least 6.25 pounds.
 21. The laminated carpetproduct of claim 20 wherein the weight of the polymers resulting fromthe reaction of polyol and isocyanate is less than 90 grams per squareyard of carpet.
 22. The laminated carpet product of claim 17 wherein thegreige comprises a tufted primary backing with a cut pile face and thetuft bind is an average of at least three pounds.
 23. The laminatedcarpet product of claim 22 wherein the weight of the polymers resultingfrom the reaction of polyol and isocyanate is less than 90 grams persquare yard of carpet.
 24. The laminated carpet product of claim 17wherein the tuft bind is an average of at least 10 pounds.
 25. Thelaminated carpet product of claim 17 wherein the polyurethane foam layercontains between 100 and 600 parts of filler for each 100 parts ofpolyol reacted to form polymers therein.
 26. The laminated carpetproduct of claim 17 wherein the polyurethane foam layer contains between250 and 550 parts of filler for each 100 parts of polyol reacted to formpolymers therein.
 27. The laminated carpet product of claim 17 whereinthe auxiliary agents include at least a catalyst and a penetrant. 28.The laminated carpet product of claim 17 wherein the weight of thepolyurethane foam layer is between 6 and 40 ounces per square yard. 29.The laminated carpet product of claim 17 wherein the weight of thepolyurethane foam layer is between 10 and 20 ounces per square yard. 30.A laminated carpet product comprising: (a) a greige having a tuftedprimary backing with a face and an opposed backstitch side; (b) a layerof polyurethane foam on the backstitch side having a weight of between10 and 20 ounces per square yard and comprising polymers resulting fromthe reaction of polyol and isocyanate prepolymers together with fillerand catalysts; (c) a spun bond polypropylene secondary backing annealedto the backstitch side by the layer of polyurethane foam; wherein theweight of the polymers resulting from the reaction of the polyol andisocyanate prepolymers is less than five ounces per square yard ofcarpet, filler is included in the polyurethane foam at a ration ofbetween 250 and 550 parts filler per 100 parts of polyol prepolymer, theaverage tuftbind of the carpet is at least 6.25 pounds, and thedelamination strength of the carpet is at least 2.5 pounds of force perinch.